This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The experiments proposed under this program will produce new insights into our understanding of the molecular mechanisms by which Bcl-2 proteins regulate the mitochondria-mediated apoptotic pathway and suggest new approaches to therapeutically modulating this process when aberrant in cancer and other diseases. We will use the Mistic protein expression technology to produce Bcl-2 proteins in active, membrane-integrated conformations at quantities sufficient for structural analysis. Advances in detergent chemistry and membrane protein crystallization techniques will facilitate high resolution X-ray structure determination of these critical apoptotic regulators in their functional conformations. This structural data will greatly improve our understanding of the means by which these proteins control mitochondria membrane permeability to regulate cellular death pathways. Greater insight into the structural mechanisms underlying the function of these proteins when in their active, membrane-integrated conformations will substantially aid the rational design of improved drugs and novel medicines for a broad variety of illnesses.